[clang] [NFC] Refactor fast-math handling for clang driver (PR #81173)

[Aaron Ballman via cfe-commits]

================
@@ -3061,22 +3080,7 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
         continue;
       [[fallthrough]];
----------------
AaronBallman wrote:

Oh! Thank you for mentioning they're in different `switch` statements, I had missed that as well. :-D

https://github.com/llvm/llvm-project/pull/81173